Focussing flexural waves for accretion removal from a beam

Abstract

Ice accretes onto structures such as aircraft wings and wind turbine blades during operation and must be removed cost effectively. In this paper, a low energy approach is proposed whereby flexural waves are focussed to create a shock response at a target point where the bond shear strength between the accretion and substrate is exceeded. Focussing is achieved through a chirp excitation waveform which compensates for wave dispersion. An experiment was performed on a long aluminium beam driven by a small electrodynamic shaker. Dispersion is seen to compress the chirp waveform in time as it propagates towards a chosen focal point, close to which the peak acceleration is maximum. An ice substitute (plaster), was accreted onto the beam and the input gain increased until the accretion debonded. Electrical energy consumption by the shaker was measured. This transient approach to accretion removal provides alternative amplification to resonance of the structure or actuator, and the focal point can be moved at will in real time.

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